Collecting behavioral data efficiently is a significant challenge faced by many auditory scientists, especially those who conduct clinical or developmental research. The prolonged process of data collection is the bottleneck restricting how much information can be gained from a single test subject and how many participants can be included in a clinical study. The long-term goal of the proposed research is to increase the efficiency of behavioral data collection, making individualized estimation of auditory psychophysical models possible. As the first step toward this goal, the estimation of two important psychophysical models will be studied in detail. The two models are the auditory filter model, a model of spectral resolution, and the cochlear input-output function, a model of peripheral nonlinearity. The parameters of these models, such as the auditory-filter bandwidth and the compression ratio of the cochlear input-output function, have been shown to be reliable indicators of cochlear health and can predict supra-threshold listening deficits. Classical procedures to fit these models use threshold-based approaches: multiple thresholds are measured, and the psychophysical model of interest is fitted using those thresholds. For the proposed procedure, a Bayesian algorithm will used to ensure that the stimulus presented on each trial is the stimulus that maximally accelerates the rate of parameter convergence. This parameter-based approach allows the estimation of the auditory filter or the cochlear input-output function using a single experimental track and fewer than 200 trials. This is approximately ten times faster than procedures currently in use. In the proposed experiments, for both of these models, parameters estimated for normal hearing listeners using the proposed and threshold-based procedures will be compared to determine the relative reliability of the new procedure. The optimal configurations for the new procedure, e.g. how to initiate and terminate an experimental track, will be identified. Additionally, the procedure developed to estimate the auditory filter will be further developed to ensure its suitability for hearing-impaired listeners. Upon the completion of the proposed research program, user-friendly software packages will be made available to hearing research community for the estimation of the auditory filter and the cochlear input-output function. The outcome of this research is expected to have a strong and sustained impact on behavioral studies of hearing and hearing impairment. With the procedures to be developed, the fitting of fundamental auditory models for individual test subjects can become routine. This will open the door to a better understanding of the individual differences in hearing capability because scientists will be able to test more participants and/or make more measurements in their experiments. Moreover, given the efficiency of the procedures, it will be much easier for the future experimenters to track a listener's hearing characteristics longitudinally.